Method for continuously tin-electroplating metal strip

Abstract

A method for continuously tin-electroplating a metal strip, which comprises the steps of: causing a DC electric current to flow between a metal strip and an anode arranged adjacent to the metal strip while passing the metal strip at a travelling speed of at least 1 m/minute through an acidic tin-electroplating solution containing tin ions and an organic acid within a range of from 4.8 to 98 g/l as converted into sulfuric acid, to form a tin-electroplating layer on at least one surface of the metal strip; and applying an ultrasonic vibration, emitted from at least one ultrasonic vibrator and having an intensity within a range of from 0.01 to 1,000 W/100 cm 2 and a frequency within a range of from 25 to 55 kHz, to the acidic tin-electroplating solution between the metal strip and the anode, thereby removing a diffusion layer of tin ions existing in the acidic tin-electroplating solution adjacent to the surface of the metal strip.

What is claimed is: 
     
       1. In a method for continuously tin-electroplating a metal strip, which comprises the steps of: causing a DC electric current to flow between a metal strip and an anode arranged adjacent to said metal strip, while passing said metal strip at a travelling speed of at least 1 m/minute through an acidic tin-electroplating solution to form a tin-electroplating layer on at least one surface of said metal strip; and   applying an ultrasonic vibration, emitted from at least one ultrasonic vibrator to said acidic tin-electroplating solution between said metal strip and said anode;   the improvement comprising: said acidic tin-electroplating solution containing tin ions and an organic acid within a range of from 4.8 to 98 g/l as converted into sulfuric acid, and a phenyl hydroxide compound within a range of from 0.1 to 5 g/l;   passing said metal strip at a travelling speed of at least 100 m/minute through said acidic tin-electroplating solution; and   said ultrasonic vibration having an intensity within a range of from 0.01 to 1,000 W/100 cm 2  and a frequency within a range of from 25 to 55 kHz;   thereby removing a diffusion layer of tin ions existing in said acidic tin-electroplating solution adjacent to the surface of said metal strip, and increasing a critical electric current density to a range of from 65 to 110 A/dm 2 .     
     
     
       2. A method as claimed in claim 1, wherein: said organic acid comprises at least one of benzene sulfonic acid, methane sulfonic acid, toluene sulfonic acid and phenol sulfonic acid.   
     
     
       3. A method as claimed in claim 1, wherein: said phenyl hydroxide compound comprises at least one of pyrocatechol, resorcinol, hydrochinone, phloroglucinol, pyrogallol and 3-aminophenol.   
     
     
       4. A method as claimed in any one of claims 1, 2 or 3 wherein: an acidic tin-electroplating solution is ejected into said acidic tin-electroplating solution between said metal strip and said anode to cause said acidic tin-electroplating solution between said metal strip and said anode to flow.